Change the default list and library experience
The new SharePoint list and library experience is faster, simpler, and responsive on mobile devices. It also supports many new capabilities that are not available in the classic experience, including Flow and PowerApps integration, the Filters pane, and column formatting. Many sites that have features or customizations that don’t work in the new experience will automatically switch back to the classic experience. For more information about this behavior, see Differences between the new and classic experiences for lists and libraries. To detect lists that won't work well with the new experience, run the SharePoint Modernization scanner.
It's no longer possible to select the classic experience as the default for all sites in your organization. Instead, we recommend setting it for only the specific sites that need it. To learn how to turn off the new list and library experience for a site collection, see Enable or disable site collection features. For info about changing this setting using PowerShell, see Opting out of the modern list and library experience.)
Users can select the default experience for an individual list or library, overriding what you set. For info, see Switch the default experience for lists or document libraries from new or classic.